US at 6 weeks - empty gestational sac

According to LMP I should be exactly 6 weeks today. Had an US this morning and the doctor said he can’t see an embryo. You can imagine how scared and sad I am now. He asked me to do a blood test for beta HCG (came back at 6300 today) and repeat it in 2 days. Then I have to go back one week from now for another ultrasound. Anyone who went through this and it all turned out fine? Also - could the 2 points on the US be the start of a yolk sac? With my first pregnancy, I could hear her heartbeat at 6w4days so I just have trouble remaining positive, any encouragement helps...